Investigations on the shale oil and gas potential of westphalian mudstone successions in the campine basin, NE Belgium (Well KB174): Palaeoenvironmental and palaeogeographical controls

Abstract

Westphalian mudstones in the Hechtel-Hoef well, Campine Basin, Belgium, were examined for their hydrocarbon potential by means of Rock-Eval pyrolysis. These mudstones have an average TOC content of 3.6% and mean S2 and Hydrogen Index values of respectively 7.9 and 164.2 mg/g and contain a mixture of kerogen types II and III. This indicates that in contrast to the Westphalian coal seams, these successions are not predominantly gas-prone but could also generate higher molecular-weight hydrocarbons and condensates. Three different palaeoenvironments, i.e. non-marine flood plains (FP), freshwater palaeoenvironment (FW), euryhaline palaeoenvironment (E) were recognised in the Westphalian mudstones, each with different hydrocarbon potential. Flood plain environments show the highest TOC and S2 values. Mudstone intervals with high TOC content occur more frequently in Westphalian A and have in general higher S2 values. The higher abundance of kerogen type II-enriched organic matter in Westphalian A indicates a lower delta plain setting. It is shown that the palaeogeographic context can be used as a proxy for the hydrocarbon generation potential of mudstone deposits from the coastal plain or of lacustrine origin.